diff --git a/optimize_mysql_tables.sh b/optimize_mysql_tables.sh
index 42b006a..6ca2c1f 100755
--- a/optimize_mysql_tables.sh
+++ b/optimize_mysql_tables.sh
@@ -240,18 +240,18 @@ fi
 [[ -z "$log_file" ]] && log_file="$DEFAULT_LOG_FILE"
 
 if [[ ${#mysql_credential_args_arr[@]} -eq 0 ]]; then
-   [[ -z "$mysql_credential_args" ]] && mysql_credential_args="$DEFAULT_MYSQL_CREDENTIAL_ARGS"
-   mysql_credential_args_arr="$mysql_credential_args"
+   mysql_credential_args_arr[0]="default:$mysql_credential_args"
 fi
 
 declare -i length_table_name
 declare -i number_blank_signd
 declare -i index_i
-for _val in ${mysql_credential_args_arr[@]} ; do
+declare -i index_arr=0
+while [[ $index_arr -lt ${#mysql_credential_args_arr[@]} ]] ; do
 
    _all_success=true
 
-   IFS=':' read -a _val_arr <<< "${_val}"
+   IFS=':' read -a _val_arr <<< "${mysql_credential_args_arr[$index_arr]}"
    mysql_version="${_val_arr[0]}"
    mysql_credential_args="${_val_arr[1]}"
 
@@ -406,6 +406,9 @@ for _val in ${mysql_credential_args_arr[@]} ; do
       echo "[ MySQL $mysql_version ]: Finished optimizing MySQL databases at host $(hostname -f)." >> $log_file
       echo "" >> $log_file
    fi
+
+   (( index_arr++ ))
+
 done
 
 if [[ ${#info_messages_arr[@]} -gt 0 ]]; then